Add Impostor.Http to the Docker image (#509)

Adding plugins to the docker image is pretty hard as you need to install
ASP.Net Core and add the plugin. As Impostor.Http has become pretty much
mandatory, install the plugin by default.

Dockerfile

@@ -34,8 +34,14 @@ RUN case "$TARGETARCH" in \
   dotnet publish -c release -o /app -r "$NETCORE_PLATFORM" -p:VersionSuffix="$VERSIONSUFFIX" --no-restore ./src/Impostor.Server/Impostor.Server.csproj
 
 # Final image.
-FROM --platform=$TARGETPLATFORM mcr.microsoft.com/dotnet/runtime:7.0
+FROM --platform=$TARGETPLATFORM mcr.microsoft.com/dotnet/aspnet:7.0
 WORKDIR /app
 COPY --from=build /app ./
-EXPOSE 22023/udp
+
+# Add Impostor.Http as a default plugin
+ADD https://github.com/Impostor/Impostor.Http/releases/download/v0.4.0/Impostor.Http.dll /app/plugins/
+# Make it listen to 0.0.0.0 to expose it to the outside world. Override ASPNETCORE_URLS to stop warning.
+ENV IMPOSTOR_HTTP_HttpServer__ListenIp=0.0.0.0 ASPNETCORE_URLS=
+
+EXPOSE 22000/tcp 22023/udp
 ENTRYPOINT ["./Impostor.Server"]